This invention relates to a sensor of the pedaling force of a power-assisting bike, particularly to one simple in structure and possible to lower producing cost as will as elevate economic gain.
A conventional pedaling-force sensor of a power-assisting bike (usually an electric bike) is provided to give out signals for a power-assisting transmission system to output motive power for a bike so as to let a rider pedal the bike with less force.
The objective of this invention is to offer a pedaling-force sensor of a power-assisting bike, simple in structure and possible to reduce producing cost and enhance economic gain.
The feature of the invention is that at least one pair of screw gears is installed in a speed-increasing system provided between the pedal cranks and the chain wheel of a bike. In this speed-increasing system, a first screw gear is actuated by the pedaling force to rotate at its original location while a second screw gear meshes with and is activated by a relative screw gear unit to move along a transmission shaft. Besides, an annular magnet device is provided at an end side of the second screw gear, capable to rotate together with the second screw gear. Then a resilience member is provided to permanently push against the annular magnet device and render it capable to return to its original position in case no motive power is supplied. Besides, the resilience member will be forced to deform by a lateral force produced when the screw gears are rotating so as to make the force balanced. Further, a Hall sensor is provided at a fixed end relative to the annular magnet device, capable to detect the variation of the position-shifting amount of the annular magnet device and measure a voltage signal representing the pedaling force. This voltage signal can control a motor installed on a bike to output motive power to drive the chain wheel of the bike.